This invention relates generally to the construction of thin films onto semiconductor surfaces and relates, more particularly, to the construction of a thin-film build-up onto semiconductor surfaces utilizing physical vapor deposition techniques.
Heretofore, much of the success of silicon metal-oxide-semiconductor (MOS) structures in microprocessor and memory technologies has been largely dependent upon the formation of well-defined SiO.sub.2 -on-silicon (abbreviated SiO.sub.2 /Si) structures wherein SiO.sub.2 serves as the gate oxide. However, for silicon MOS devices, including silicon metal-oxide-semiconductor field effect transistor (MOSFET) devices, there is considerable interest in replacing SiO.sub.2 with a deposited dielectric material possessing a higher dielectric constant. Furthermore, semiconductor materials--other than those which include silicon--are likely to become attractive for use in digital switching applications if methods are developed for forming well-defined oxide/semiconductor interfaces suitable for functional MOS-type structures. For example, Ge is an attractive semiconductor material for microelectronic applications because Ge possesses higher carrier mobility and a higher thermal conductivity than that of silicon. However, the native germanium oxides are not suitable for MOS-type device structures because these oxides are not very stable. With this in mind, the formation of stable metal oxides on Ge could prove instrumental in the development of Ge surfaces, as well as other non-silicon-including semiconductor surfaces, for use in integrated circuit applications.
For the development of MOS devices which employ a thin-film oxide disposed directly atop a semiconductor material other than silicon for use in applications, such as can include sensor, photovoltaic and optoelectronic applications, the formation of well-defined metal oxide/semiconductor interfaces is of paramount importance. Within the structure of many of such devices, it is preferable that the metal oxide/semiconductor interface be devoid of any native oxide, since the presence of native oxide at the interface is likely to limit the performance of these structures. Accordingly, it would be desirable to provide a method for constructing a thin-film build-up of metal oxide onto a semiconductor surface, other than a surface which includes silicon, wherein the growth of native oxides at the surface/metal oxide interface is minimized. By definition, a native oxide is that oxide (or oxides) which spontaneously forms on the material surface when the material surface is exposed to oxygen at elevated temperatures.
Accordingly, it is an object of the present invention to provide a new and improved method for growing thin-film metal oxide upon a semiconductor surface, other than a surface which includes silicon, which reduces the likelihood that native oxides will form at the surface/oxide interface and structures formed with the method.
Another object of the present invention is to provide such a method which utilizes physical vapor deposition techniques.
Still another object of the present invention is to provide such a method for growing a thin-film metal oxide upon the underlying semiconductor surface wherein the thin-film growth can be used as a template for additional film growth.
Yet another object of the present invention is to provide such a method which is uncomplicated to perform.